This invention relates to a high pressure fluid delivery system for water blasting equipment using fluid pressures in the range of 10,000 to 20,000 psig or more. One of the principal aspects of the invention relates to a fail-safe fluid delivery system which employs series connected and redundant shut-off valves so that upon release of the gun trigger high pressure fluid flow through the gun tip will cease, even if one of the series connected shut-off valves should fail to operate. Another aspect of the invention is to a novel fluid delivery system which is particularly adaptable to a system of multiple high pressure water blasting guns which are fed from a single high pressure water delivery manifold and pump.
In typical prior art systems it is conventional to employ a so-called "dump gun" wherein the high pressure fluid is dumped at the gun prior to operation of the gun trigger mechanism. Typically such guns employ a trigger operated shut-off valve integral with the gun assembly which is physically controlled by the operator. In relatively low pressure water blasting equipment such mechanisms are reasonably suitable since the operator can physically and readily apply the necessary mechanical force to open or close the valve in the presence of the fluid pressure being delivered by the pump. However, as pump discharge pressures have increased to the 20,000 psig discharge range multiple dump guns with a single pump supply are not suitable because dumping of any one gun would deprive the other guns of fluid pressure. Accordingly, alternative control systems for the water blast gun have been devised wherein an electrical switch has been actuated by the gun trigger mechanism to remotely control a solenoid to pneumatically actuate a shut-off valve to supply high pressure liquid directly to the gun. These systems, therefore, did not dump the pressurized fluid at the operator's work station through the gun, but would relieve the pump discharge pressure either at the pump or some other location of the electrically operated pneumatic controlled dump valve. In each of these systems, however, only a single shut-off valve was employed for the control of the high pressure fluid discharged through the gun. While systems of this type have proved adequate for water blasting in the lower discharge pressure ranges, the advent of higher and higher pressure pumps in the range of 20,000 psig discharge pressure has made it more important that the operator be assured that the water blast gun will be shut-off upon his release of the gun trigger. The reason for this is that as the water blasting pressures have increased to these higher ranges the blast gun operator will shoulder the gun with ever increasing manual force to compensate for the higher discharge pressures. Upon shut-off of the gun by release of the trigger mechanism the reaction force immediately ceases and the gun operator must be alert not to fall over forward upon stopping of the gun blast. Accordingly, from experience, the gun operator expecting that the water blast will cease upon his release of the gun trigger, will automatically anticipate such and will lean back so that he does not fall forward upon stopping of the water blast from the gun nozzle. In the unlikely event that the shut-off valve, for one reason or another, does not stop the water blast upon release of the gun trigger an experienced operator, expecting such to occur, however, may fall over backwards in anticipation of the reduced force he is expecting from the gun. Accordingly, as water blasting pressures have increased more operator lean into the work piece has occurred and, accordingly, great reliance is placed by the operator on the gun trigger mechanism that it will be effective to shut-off the water flow through the gun nozzle when the trigger is released. Therefore, it has become considerably more important that as water discharge pressures have increased that the fluid delivery system be such as to assure the operator that shut-off will occur when he expects it to shut-off. Examples of prior art systems disclosed herebefore may be seen in applicant's prior U.S. Pat. Nos. 3,986,523 and 3,831,845.